Zinc-Silver Mine and the Gold Potential of Novo Brdo/Artana Tailings (Kosovo) Final Report
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French scientific cooperation 2007-2008 on the Trepča lead- zinc-silver mine and the gold potential of Novo Brdo/Artana tailings (Kosovo) Final Report BRGM/RP-57204-FR October, 2009 French scientific cooperation 2007-2008 on the Trepča lead- zinc-silver mine and the gold potential of Novo Brdo/Artana tailings (Kosovo) Final Report BRGM/RP-57204-FR October, 2009 Study carried out as part of Research activities of BRGM 2007 J. Féraud, Y. Deschamps Checked by: Approved by: Name: Th. Augé Name: D. Artignan Date: October 5th, 2009 Date: October 12th, 2009 Signature: Signature: If the present report has not been signed in its digital form, a signed original of this document will be available at the information and documentation Unit (STI). BRGM’s quality management system is certified ISO 9001:2000 by AFAQ. (Front cover photo) Pseudo-stalactite (without axial feeder pipe) of rhodochrosite, galena, sphalerite, calcite, 5 cm wide, Stari Trg mine (old collection). Keywords: Ore deposits; Tailing; Mining residue; Valorization; Skarn; Karst; Pb-Zn-Ag ore deposit; Hydrothermal-metasomatic; Low sulfidation; Gold; Indium; Hydraulic breccia; Hydrothermal breccia; Fluidised breccia; Maar volcanism; Phreatomagmatic breccia; Neogene; Museography; Kosovo. In bibliography, this report should be cited as follows: Féraud, J., Deschamps Y. (2009) – French scientific cooperation 2007-2008 on the Trepča lead-zinc-silver mine and the gold potential of Novo Brdo/Artana tailings (Kosovo). BRGM report No. RP-57204-FR, 92 p., 13 figs, 4 tabl., 18 photos, 1 appendix. © BRGM, 2009. No part of this document may be reproduced without the prior permission of BRGM. French cooperation 2007-2008 on Trepča mine (Kosovo) Synopsis The world-famous Trepča mine (also renowned as the Trepča Stari Trg or Stan Terg mine) has yielded 2 Mt lead and 1.5 Mt zinc, 2,500 t silver, 4,000 t bismuth and 9 t gold. After the war of Kosovo, the mine has resumed Pb and Zn-concentrates production since September 2005 and is currently offered to foreign investment. exploration restarts on promising deposits like Novo Brdo as well. A close cooperation between BRGM and Trepča has developed. In 2007, it partly benefited of a grant from the Research directorate of BRGM (project n° PDR07REM06 entitled “valorization of the high-tech metals of the Balkans”). The present report aims at presenting an overall summary of the results currently obtained from this cooperation, within the global advances of knowledge presently reached by the Trepca geologists and mineralogists and by the other scientists who are working in the area. The Trepča Stari Trg ore deposit was the main focus of the 2007-2008 cooperation. New data and observations now available lead to a geological appraisal of the deposit, concerning its geodynamic setting, its geological controls and metallogenic model, and its trace elements and particularly precious (silver, gold) and rare metals content (bismuth, indium, etc.). The valuable elements in the ore concentrates and flotation tailings of Stari Trg and some other mines have been investigated as well. Finally, concerning mineralogy, geological heritage and museography, a close cooperation has been settled in view of helping the famous Crystal Museum of Trepča to recover the world rank it deserves. From the geodynamic point of view, the Trepča Stari Trg ore deposit is located in the western branch of the Alpine-Balkan-Carpathian-Dinaride belt (ABCD belt), in the External Vardar Subzone (EVSZ of the current authors). It belongs to the carbonate replacement deposits type, but it may also be considered as the polymetallic root of an eroded low-sulphidation epithermal type system as well. It comprises a series of manto orebodies and mineralized skarns within the Jurassic sedimentary carbonate platform known as the Stari Trg series. These orebodies form a hose shaped envelope at the contact with an Oligo-Miocene dacitic volcanic conduit partially brecciated. Within this envelope, the deeper parts of the ore deposit visible at present have led both Trepca and BRGM geologists to identify hydraulic brecciation by hydrothermal explosions within the marmorised limestones hosting the mineralisation. A phreatomagmatic breccia is evidenced in the conduit (diatreme). BRGM/RP-57204-FR – Final report 3 French cooperation 2007-2008 on Trepča mine (Kosovo) Therefore, within the regional frame of Oligo-Miocene volcanism with ignimbrites and calderas, the existence of maar-type hydrovolcanic deep explosions along the Trepča volcanic diatreme, connected with its plumbing system acting as a hydrogeological trap for the mineralised mantos and skarns, is evidenced. The age and role of the karstification itself in the metallogenetic process is discussed in the light of new observations. Finally, the analyses performed on the run of mine of Trepca Stan Terg, on the ore bodies of the lower levels and on three batches of Zn and Pb ore concentrates assessed significant contents of Ag, Bi, Cu and Au, with indications of In, Te, Ga and Tl. The increasing abundance of In together with other rare metals downdip suggests that valorisation of selective mining of elevated grades could be profitable in the next years. The other focus of the 2007-2008 cooperation was the Novo Brdo (Artana) ore deposit. It has enlightened in particular the (relative) abundance of indium in this deposit (200 g/t In within the zinc-concentrate). Moreover, the high grade in the old tailings of Artana/Novo Brdo particularly of gold, already identified by the geologists of Trepča, is confirmed (possibly up to 2.5 g/t Au). They represent a potential target the order of magnitude of which could reach 21 Mt ore containing hypothetically around 30 t Au and 300 t Ag. According to the last BRGM laboratory scale tests still currently in progress, this target appears hampered by the lack of free gold and by its location within the iron sulphides (pyrite, pyrrhotite). Additional studies of these tailings (and of the other tailings dams and slags heaps not yet sampled in the whole Trepča district) are recommended. Thus the mining activities of this historical district could be developed, whereas the environmental impacts of its old tailings dams could be reduced. 4 BRGM/RP-57204-FR – Final report French cooperation 2007-2008 on Trepča mine (Kosovo) Contents 1. General framework and scope of the cooperation ..................................11 1.1. TREPCA MINE AND TREPCA ORE DISTRICT : MAIN FEATURES, IMPORTANCE...................................................................................................11 1.1.1. Exact name of the ore deposit..................................................................11 1.1.2. Location ....................................................................................................11 1.1.3. Importance and interest............................................................................11 1.2. HISTORY OF THE COOPERATION OF FRENCH INSTITUTIONS WITH TREPČA MINE AND ITS PEOPLE....................................................................15 1.3. ORGANISATION OF THE 2007-2008 COOPERATION ...................................18 1.4. WORK PERFORMED........................................................................................19 2. Geodynamic setting of the Trepča/Stan Terg ore deposit ......................21 2.1. STRUCTURAL FRAMEWORK..........................................................................21 2.2. STRATIGRAPHIC EMPLACEMENT OF THE ORE DEPOSIT, METAMORPHISM .............................................................................................23 2.3. MAGMATISM AND ITS REGIONAL METALLOGENIC ROLE ..........................24 3. Geological controls on mineralisation and metallogenic model............27 3.1. GEOMETRY OF THE ORE DEPOSIT, MINERAL ASSEMBLAGE, HYDROTHERMAL ALTERATIONS...................................................................27 3.2. GEOMETRY OF THE OTHER PB-ZN PROSPECTS AROUND TREPČA .......31 3.3. AGE AND METALLOGENIC CLASSIFICATION OF TREPČA .........................34 3.3.1. Role of magmatism and volcanism...........................................................34 BRGM/RP-57204-FR – Final report 5 French cooperation 2007-2008 on Trepča mine (Kosovo) 3.3.2. New observations: identification of hydraulic explosion breccias............. 35 3.3.3. Role and place of karstification ................................................................ 38 4. Ore composition, trace elements, precious and rare metals of Stan Terg41 4.1. ZINC, LEAD, SILVER........................................................................................ 41 4.2. COPPER ........................................................................................................... 42 4.3. BISMUTH .......................................................................................................... 43 4.4. CADMIUM ......................................................................................................... 43 4.5. GOLD ................................................................................................................ 43 4.6. TUNGSTEN AND TIN ....................................................................................... 44 4.7. INDIUM AND OTHER RARE METALS ............................................................. 44 4.8. URANIUM.......................................................................................................... 45 4.9. PERSPECTIVES AND RECOMMENDATIONS................................................ 45 5. Valorization of